The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Powertrain systems use transmission devices to transfer tractive torque between one or more torque generative devices and an output member connected to a driveline. A hybrid transmission device transfers torque between multiple torque generating devices and an output member, with the multiple torque generating devices configured to generate power by converting potential energy to mechanical power. The hybrid transmission device and torque generating devices can also operate to react vehicle kinetic energy to create storable potential energy.
One of the torque generating devices can include a reciprocating piston internal combustion engine. A transmission device transfers mechanical power in the form of speed and torque from the engine to a driveline. The hybrid powertrain system can permit engine operation that is somewhat independent from the power output from the transmission, deriving additional power to meet requirements from other torque-generating devices. This permits engine operation that is optimized for emissions and fuel efficiency. A power-split transmission can use differential gearing to achieve a continuously variable torque and speed ratio between input and output. An electrically variable transmission can use the differential gearing to send a portion of the transmitted power to one or more torque generating devices, with a remainder of the power sent through a parallel torque path to a driveline. One form of differential gearing includes a planetary gear set.